Impurity-induced seeding of polycrystalline semiconductors

A semiconductor fabrication process improves the crystal structure of a polycrystalline semiconductor. Adding impurities in large quantities causes an acceleration of the crystallization without noticeably increasing the number of spontaneous nucleations in the material. The result is a region of relatively larger crystalline grains within the doped region which extend approximately 1 mu m into the undoped region by the time the entire material has crystallized. Junction devices can be created with better electrical characteristics than ordinary polycrystalline semiconductor devices due to fewer grain boundaries at the electrical junctions. One fabrication technique can result in single crystal devices. Another implementation shows a method for fabricating improved polycrystalline vertical diodes such as solar cells.